[llvm] b488ce0 - [memprof] Improve call site matching (#129770)

[via llvm-commits]

Author: Kazu Hirata
Date: 2025-03-04T21:09:40-08:00
New Revision: b488ce0a677b42179198ea00bc6e860baa9874e3

URL: https://github.com/llvm/llvm-project/commit/b488ce0a677b42179198ea00bc6e860baa9874e3
DIFF: https://github.com/llvm/llvm-project/commit/b488ce0a677b42179198ea00bc6e860baa9874e3.diff

LOG: [memprof] Improve call site matching (#129770)

Suppose we have a call instruction satisfying:

- AllocInfoIter != LocHashToAllocInfo.end()
- CallSitesIter != LocHashToCallSites.end()
- !isAllocationWithHotColdVariant(CI->getCalledFunction(), TLI)

In this case this patch, we would take:

  if (AllocInfoIter != LocHashToAllocInfo.end()

but end up discarding the opportunity because of the call to
isAllocationWithHotColdVariant.

This can happen in C++ code like:

  new Something[100];

which is lowered to two calls -- new and the constructor.

This patch fixes the problem by falling back to the call site
annotation if we have !isAllocationWithHotColdVariant.

Added: 
    llvm/test/Transforms/PGOProfile/memprof-call-site-at-alloc-site.ll

Modified: 
    llvm/lib/Transforms/Instrumentation/MemProfiler.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp b/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
index a0a5834731c2e..71a0b29f82a7e 100644
--- a/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
@@ -1122,10 +1122,9 @@ readMemprof(Module &M, Function &F, IndexedInstrProfReader *MemProfReader,
       // instruction's leaf location in that map, and if the rest of the
       // instruction's locations match the prefix Frame locations on an
       // allocation context with the same leaf.
-      if (AllocInfoIter != LocHashToAllocInfo.end()) {
-        // Only consider allocations which support hinting.
-        if (!isAllocationWithHotColdVariant(CI->getCalledFunction(), TLI))
-          continue;
+      if (AllocInfoIter != LocHashToAllocInfo.end() &&
+          // Only consider allocations which support hinting.
+          isAllocationWithHotColdVariant(CI->getCalledFunction(), TLI)) {
         // We may match this instruction's location list to multiple MIB
         // contexts. Add them to a Trie specialized for trimming the contexts to
         // the minimal needed to disambiguate contexts with unique behavior.
@@ -1189,10 +1188,12 @@ readMemprof(Module &M, Function &F, IndexedInstrProfReader *MemProfReader,
         continue;
       }
 
+      if (CallSitesIter == LocHashToCallSites.end())
+        continue;
+
       // Otherwise, add callsite metadata. If we reach here then we found the
       // instruction's leaf location in the callsites map and not the allocation
       // map.
-      assert(CallSitesIter != LocHashToCallSites.end());
       for (auto CallStackIdx : CallSitesIter->second) {
         // If we found and thus matched all frames on the call, create and
         // attach call stack metadata.

diff  --git a/llvm/test/Transforms/PGOProfile/memprof-call-site-at-alloc-site.ll b/llvm/test/Transforms/PGOProfile/memprof-call-site-at-alloc-site.ll
new file mode 100644
index 0000000000000..0a51128a7fcef
--- /dev/null
+++ b/llvm/test/Transforms/PGOProfile/memprof-call-site-at-alloc-site.ll
@@ -0,0 +1,52 @@
+; Verifies that a call site gets annotated even when a call site matches an
+; allocation call stack but does not call one of the memory allocation
+; functions.
+
+; REQUIRES: x86_64-linux
+; RUN: split-file %s %t
+; RUN: llvm-profdata merge %t/memprof-call-site-at-alloc-site.yaml -o %t/memprof-call-site-at-alloc-site.memprofdata
+; RUN: opt < %t/memprof-call-site-at-alloc-site.ll -passes='memprof-use<profile-filename=%t/memprof-call-site-at-alloc-site.memprofdata>' -memprof-print-match-info -S 2>&1 | FileCheck %s
+
+;--- memprof-call-site-at-alloc-site.yaml
+---
+HeapProfileRecords:
+  - GUID:            _Z3foov
+    AllocSites:
+      - Callstack:
+          - { Function: _Z3foov, LineOffset: 6, Column: 12, IsInlineFrame: false }
+        MemInfoBlock:
+          AllocCount:      1
+          TotalSize:       898709270
+          TotalLifetime:   1000000
+          TotalLifetimeAccessDensity: 1
+    CallSites:
+      - - { Function: _Z3foov, LineOffset: 6, Column: 12, IsInlineFrame: false }
+...
+
+;--- memprof-call-site-at-alloc-site.ll
+; CHECK: MemProf callsite match for inline call stack 774294594974568741
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-grtev4-linux-gnu"
+
+declare void @_ZN9SomethingC1Ev()
+
+define void @_Z3foov() {
+  %1 = call ptr @_Znam(), !dbg !3
+  call void @_ZN9SomethingC1Ev(), !dbg !3
+  ret void
+}
+
+declare ptr @_Znam()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1)
+!1 = !DIFile(filename: "something.cc", directory: "/")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !DILocation(line: 106, column: 12, scope: !4)
+!4 = distinct !DISubprogram(name: "Init", linkageName: "_Z3foov", scope: !5, file: !1, line: 100, type: !7, scopeLine: 100, spFlags: DISPFlagDefinition, unit: !0)
+!5 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "Something", file: !1)
+!6 = !{}
+!7 = distinct !DISubroutineType(types: !6)